Guaranteed admission and incremental bandwidth allocation in a packet network

ABSTRACT

In a packet network, a feature wherein each node in the call path grants immediate admission to the network at a possibly reduced or even zero initial bandwidth. Additional bandwidth is incrementally allocated to the call as it becomes available until the maximum requested bandwidth has been allocated to the call for each node in the call path.

FIELD OF INVENTION

[0001] The present invention relates to the field of packet networks,and more particularly to the area of bandwidth allocation during asession or connection.

BACKGROUND OF THE INVENTION

[0002] In a packet network, a scheme must be implemented to avoidcongestion. A simple solution would be to over-engineer the network suchthat congestion is not a problem. While this will serve to alleviatecongestion, it can be very expensive and is often a short-term solutionat best, as additional traffic growth can quickly overwhelm the network.Other solutions are typically network based and fall under thecategories of bandwidth and traffic management. An example of trafficmanagement would be routing packets over an alternate path in thenetwork to avoid network elements that are experiencing congestion. Anexample of bandwidth management would be the network negotiating with anend user during session setup such that the bandwidth allocated to theend user will not exceed a given value and will not negatively affectalready established sessions.

[0003] A brief discussion of network bandwidth management for threepopular representative multimedia packet protocols is presented below.The protocols are: H.323 Packet-Based Multimedia Communications Systems,Session Initiation Protocol (SIP), and Asynchronous Transfer Mote (ATM).

H.323 Packet-Based Multimedia Communications Systems

[0004] The H.323 protocol describes terminals and other entities thatprovide multimedia communications services over packet networks whichmay not provide a guaranteed quality of service. H.323 entities mayprovide real-time audio, video and/or data communications. Support foraudio is mandatory, while data and video are optional. If data and videoare supported, the ability to use a specified common mode of operationis required, so that all terminals supporting that media type caninterwork.

[0005] The packet based network over which H.323 entities communicatemay be a point-to-point connection, a single network segment, or aninternetwork having multiple segments with complex topologies.

[0006] H.323 entities may be used in point-to-point, multipoint, orbroadcast configurations. They may interwork with H.310 terminals onB-ISDN, H.320 terminals on N-ISDN, H.321 terminals on B-ISDN, H.322terminals on Guaranteed Quality of Service LANs, H.324 terminals on GSTNand wireless networks, V.70 terminals on GSTN, and voice terminals onGSTN or ISDN through the use of Gateways. H.323 entities may beintegrated into personal computers or implemented in stand-alonecustomer premise equipment (CPE) devices such as videotelephones.

[0007] Operation of a H.323 network is described, inter alia, instandards publications “H.323 Packet-Based Multimedia CommunicationsSystems,” November 2000, and “H.225.0 Call Signalling Protocols andMedia Stream Packetization for Packet-Based Multimedia CommunicationSystems,” November 2000, both published by the TelecommunicationStandardization Sector of the International Telecommunication Union(ITU-T), and both hereby incorporated by reference.

[0008] In a typical H.323 network, H.323 endpoints, or terminals, gainaccess to the network through the services of a Gatekeeper. Among itsmany functions, a Gatekeeper performs Admission Control in which itauthorizes network access based on criteria that include bandwidth, andBandwidth Control in which it authorizes changes in bandwidth for H.323calls. The Gatekeeper can control of the number of H.323 terminalspermitted simultaneous access to the network, and may reject calls froma terminal due to bandwidth limitations. This may occur if theGatekeeper determines that there is not sufficient bandwidth availableon the network to support the call.

[0009] In call setup, requests for bandwidth reservation should takeplace at the earliest possible phase. A terminal requests access to thenetwork by sending an H.225 Admission Request (ARQ) message to theGatekeeper. Included in the ARQ message parameters are bandwidth andcallType. Parameter bandwidth indicates the bi-directional bandwidthrequested for the call, in units of 100 bits per second. For example, a128 kbit/s call would be signaled as a request for 256 kbit/s. The valuerefers only to the audio and video payload bit rate excluding headersand overhead. Parameter callType can be used by the Gatekeeper toattempt to determine “real” bandwidth usage.

[0010] If the Gatekeeper determines that the network has sufficientavailable bandwidth to accommodate the terminal's requested bandwidth inthe ARQ record (as well as the other capabilities requested by theterminal), the Gatekeeper responds to the terminal with an AdmissionConfirm (ACF) message, and call setup proceeds or concludes. In someimplementations, the ACF message contains an allowed maximum bandwidthfor the call that may be less than the requested bandwidth in the ACQrecord. If the Gatekeeper determines that there is not sufficientavailable network bandwidth to accommodate the terminal's requestedbandwidth, then the Gatekeeper responds to the terminal with anAdmission Reject (ARJ) message.

[0011] The H.323 protocol also allows terminals to request of theGatekeeper, and the Gatekeeper to request of terminals, changes inbandwidth. This is accomplished by a terminal sending an H.225 BandwidthRequest (BRQ) message to the Gatekeeper, and the Gatekeeper respondingto the terminal with either a Bandwidth Confirm (BCF) message, or aBandwidth Reject (BRJ) message, based on current network bandwidthavailability as seen by the Gatekeeper at the time the BRQ message isreceived. Or, the Gatekeeper sending a BRQ message to a terminal, andthe terminal responding to the Gatekeeper with either a BCF message or aBRJ message.

Session Initiation Protocol (SIP)

[0012] Session Initiation Protocol (SIP) is an application-layertext-based control protocol that can establish, modify and terminatemultimedia sessions or calls. These multimedia sessions includemultimedia conferences, distance learning, Internet telephony andsimilar applications. SIP can “invite” both persons and “robots”, suchas a media storage service, to a session. SIP can invite parties to bothunicast and multicast sessions; the initiator does not necessarily haveto be a member of the session to which it is inviting. Media andparticipants can be added to an existing session. SIP can be used toinitiate sessions as well as invite members to sessions that have beenadvertised and established by other means.

[0013] Session Description Protocol (SDP) is used in conjunction withSIP for describing multimedia sessions for the purposes of sessionannouncement, session invitation, and other forms of multimedia sessioninitiation.

[0014] SIP and SDP are described in the Internet Engineering Task Forcestandards documents “RFC 2543—SIP: Session Initiation Protocol,” March1999, and “RFC 2327—SDP: Session Description Protocol,” March 1999, bothpublished by The Internet Society, and both hereby incorporated byreference.

[0015] A successful two-party call setup consists of two messages: anINVITE followed by an ACK. The INVITE message asks the callee to join acall. After the callee has agreed to participate in the call, the callerconfirms that it has received that response by sending an ACK message.

[0016] The INVITE request typically contains a session descriptionwritten in SDP format that provides the called party with enoughinformation to join the call. The session description enumerates themedia types and formats that the caller is willing to use and where itwishes the media data to be sent. If the callee wishes to accept thecall, it responds to the invitation by returning a similar sessiondescription listing the media it wishes to use.

[0017] The ACK request may contain a message body with the final sessiondescription to be used by the callee. If the ACK message body is empty,the callee uses the session description in the INVITE request.

[0018] Changes to existing calls, including increasing or decreasingmaximum bandwidth, may be made through the exchange of a new set ofINVITE and ACK messages, based on availability at the time the newINVITE message is sent.

[0019] Among the session descriptors of the INVITE message is abandwidth type descriptor (“b=”). This specifies the proposed maximumbandwidth to be used by the call, as expressed in kilobits per second.Negotiation between the caller and callee for an acceptable bandwidth ispossible. Lower layer network protocols can also negotiate or reject thecall based on network bandwidth considerations.

Asynchronous Transfer Mode (ATM)

[0020] An ATM network consists of ATM nodes connected by point-to-pointATM links. Each ATM node supports user-network interfaces (UNI) andnetwork-node interfaces (NNI). UNI are interface points between ATM endusers and private ATM nodes, or between private ATM nodes and the publiccarrier ATM network. NNI are any physical or logical links across whichtwo ATM nodes exchange the NNI protocol.

[0021] ATM networks transmit information in fixed length 53-byte cellsthat are comprised of a 5-byte header and a 48-byte payload. A lowerlevel protocol layer called the ATM Adaptation Layer (AAL) isresponsible for the segmentation and reassembly of longer message typesfrom higher level protocol layers.

[0022] ATM networks are fundamentally connection oriented. A virtualcircuit, comprising a series of connections between nodes, needs to beset up across the ATM network before any data is exchanged between endusers. Connections between nodes are referred to as virtual paths andvirtual channels. A virtual channel is a connection between twocommunicating ATM users. All communications between the two users forthe duration of the session takes place over the established virtualchannel. A virtual path is a bundle of virtual channels that is carriedbetween two points in the ATM network. A virtual channel may traversemany virtual paths in the ATM network. In the ATM cell header, thevirtual channel identifier (VCI) and the virtual path identifier (VPI)have local significance only across a particular link between nodes, andare remapped, as appropriate, at each node.

[0023] An ATM user desiring to establish a connection with another usersends a connection request signaling message containing the calling andcalled party addresses to the network. Based on the called partyaddress, the signaling is routed through the network node-by-nodesetting up connection identifiers until it reaches the destination enduser. The destination end user can either accept and confirm theconnection request, or can reject it and clear the connection. Becausethe connection is set up along the path of the connection request, thecall data also flows along this same path.

[0024] Operation of an ATM node is basically very simple. The nodereceives a cell across a link on a known VCI/VPI value. The node thenlooks up the connection value in a local translation table to determinethe outgoing port (or ports) of the connection and the new VCI/VPI valueof the connection on that link. The node then retransmits the cell onthat outgoing link with the appropriate connection identifiers. Onereason that the basic node operation is so simple is because theconnection values in the local translation tables are establishedautomatically through the signaling protocol during the connectionrequest signaling function before the transmittal of any data.

[0025] During call setup, a user requesting a connection can request acertain bandwidth and Quality of Service (QoS) from the network and canbe assured that the network will deliver that bandwidth and QoS for thelife of the connection. When a connection request is received by thenode, the node performs a function known as Connection Admission Control(CAC). Based upon the traffic parameters and requested QoS of theconnection, the node establishes the connection only if it will notresult in the violation of QoS guarantees of already establishedconnections. The CAC function is aided by a feature of the ATM protocolin which nodes flood QoS and reachability information so that all nodesobtain knowledge about reachability within the network and the availabletraffic resources within the network.

[0026] Operation of the ATM protocol is described, inter alia, instandards publications “ATM User-Network Interface (UNI) SignallingSpecification,” Version 4.0, af-sig-0061.000, July 1996, and “TrafficManagement Specification,” Version 4.1, AF-TM-0121.000, March 1999, bothpublished by The ATM Forum, and ITU-T Q.2931, “Broadband IntegratedServices Digital Network (B-Isdn)—Digital Subscriber Signalling SystemNo. 2 (DSS 2)—User-Network Interface (UNI) Layer 3 Specification ForBasic Call/Connection Control,” published by the TelecommunicationStandardization Sector of the International Telecommunication Union(ITU), February 1995, all thereof which are hereby incorporated byreference.

[0027] The three protocols described above, and indeed most packetprotocols, share some common characteristics in regards to theirtreatment of bandwidth management. In all these protocols, an end userrequests admission to the network, specifying certain sessionrequirements such as maximum bandwidth and QoS. In all these protocols,there is some form of an admission control function whereby the networkdetermines if the user connection request can be satisfied withoutadversely affecting network congestion. If the network cannotaccommodate the user connection, the request is rejected. If the networkcan accommodate the user connection, admission is granted and the useris generally limited to the maximum bandwidth requested. Usually,bandwidth changes may be requested, based on availability at the timethat the request is made.

[0028] With greater integration and utilization of multimedia packetprotocols comes greater reliance on these networks. There is a problemin the existing multimedia packet protocols in that during periods ofnetwork congestion, connections that a user might deem as importantcould be rejected through the admission control function. It would bedesirable to the user, and a source of revenue to the service provider,if there were a premium service offering available in which a subscribercould be guaranteed admission to the network, at a possibly reducedinitial bandwidth allocation, and incrementally allocated the requestedbandwidth as bandwidth becomes available.

SUMMARY OF THE INVENTION

[0029] Accordingly, it is an object of the present invention to providea service feature to packet network sessions such that such a sessionwill be guaranteed admission to the network, at a possibly reducedinitial bandwidth allocation, and incrementally allocated additionalbandwidth as bandwidth becomes available until the session has beenallocated the requested bandwidth.

[0030] The present invention is an enhanced service offering in a packetnetwork that is implemented in the end user node as well as each packetnode of the call path. The service offering provides subscribersimmediate admission to the network at a possibly reduced, or even zero,initial bandwidth. Each node in the call path grants the subscriberimmediate admission to the network at a possibly reduced, or even zero,initial bandwidth. If the user's requested maximum bandwidth is notavailable at the time of call setup, then additional bandwidth isincrementally allocated to the call as it becomes available until therequested bandwidth has been allocated for each node along the callpath.

DESCRIPTION OF THE DRAWINGS

[0031] The FIGURE shows a block diagram of a general embodiment of thepresent invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0032] The guaranteed admission and incremental bandwidth feature of thepresent invention is a service offering in packet networks that allows acall (or session or connection) to receive immediate access to thenetwork with a possibly reduced or zero initial bandwidth allocation. Ifthe call is not initially allocated the requested bandwidth, the callreceives one or more additional bandwidth allocations as bandwidthbecomes available until the call has been allocated the maximumbandwidth requested. Bandwidth allocation to the call is not reducedduring the period that the call is active.

[0033] This feature is implemented as a protocol enhancement on networknodes, such as switches, routers, gatekeepers, user terminals, etc. Thespecific encoding of the protocol messages will vary by protocol, andhardware implementations may vary by user terminal and nodemanufacturer. Not all nodes in a network are required to have thefeature. The feature is at least required on some nodes in the call pathfor the feature to apply on those portions of the call path. If allnodes in the call path do not have the feature, then the call may bedenied access to the network if bandwidth is not available at thosenodes that do not have the feature. In the preferred embodiments, allnodes in the call path have the feature. Implementations should becompatible with existing protocols.

[0034] All implementations share some common attributes. In thepreferred embodiment, the subscriber's source user terminal initiatesthe call to a destination user terminal and sets an indicator in a callsetup message indicating that the guaranteed admission and incrementalbandwidth feature is requested. There may be several call setup messagesexchanged between the source user terminal, the destination userterminal and the network. It is preferable that the indicator be in thefirst message that results in the initiation of call admission to thenetwork.

[0035] Each node in the call path will recognize the guaranteedadmission and incremental bandwidth feature indicator in callsrequesting the feature. The edge node, to which the user terminal isconnected, or another node in the call path may execute a verificationroutine to verify that the user subscribes to the feature.

[0036] Each node in the call path will preserve and convey theguaranteed admission and incremental bandwidth feature indicator in thecall setup message to the next node in the call path.

[0037] The call setup message will contain an explicit or implicitmaximum bandwidth request. The maximum bandwidth request may be in theform of a specific code or value, or may be implied based on other callparameters, such as requested quality of service.

[0038] A node cannot reject a guaranteed admission and incrementalbandwidth feature call because of bandwidth allocated to otherconnections. A node may reject a connection due to other reasons. A nodemay “suggest” a less congested route.

[0039] Each node will admit the call to the network with an initialbandwidth allocation that may be less than the maximum bandwidthrequested in the session setup message. This initial bandwidthallocation may be zero.

[0040] Each node will automatically incrementally allocate to theguaranteed admission and incremental bandwidth feature call newlyavailable user bandwidth up to the requested maximum bandwidth asbandwidth becomes available if the call was initially allocated lessthan the maximum bandwidth requested. Equitable allocation schemes maybe established to allocate newly available bandwidth among guaranteedadmission and incremental bandwidth feature calls.

[0041] The above common characteristics describe a system where anend-to-end call path is established for guaranteed admission andincremental bandwidth feature calls, even though some nodes in the callpath may not have enough bandwidth available to satisfy the call'srequested maximum bandwidth. Some nodes in the call path may have noavailable bandwidth at the time of call admission. Generally, a nodewill not deny admission to the network for guaranteed admission andincremental bandwidth feature calls. Exceptions to this rule include,for example, situations where the network is damaged. Regarding theallocation of bandwidth to guaranteed admission and incrementalbandwidth feature calls as bandwidth becomes available, allocationschemes may be developed at a node or network level that allocate newlyavailable bandwidth in an equitable manner. For example, all guaranteedadmission and incremental bandwidth feature calls may be allocated anequal percentage of newly available bandwidth, or the oldest calls maybe allocated bandwidth first. Other calls having a higher priority thanthe guaranteed admission and incremental bandwidth feature call may beallocated bandwidth first.

[0042] Most protocols handle call setup bandwidth allocation requestsand subsequent bandwidth change requests instantaneously, i.e.,bandwidth allocation and change requests are granted or rejected basedon available bandwidth at the time of the request. With the guaranteedadmission and incremental bandwidth feature, each network will have somemechanism to track feature calls that have not received bandwidthallocation up to the requested maximum. Specific implementations canvary by protocol and node. In the preferred embodiment, each node willmaintain a means to track guaranteed admission and incremental bandwidthfeature calls that have not been allocated bandwidth up to theirrequested maximum. The means to track can include, but is not limitedto, such mechanisms as tables, queues, lists, etc.

[0043] The guaranteed admission and incremental bandwidth feature isapplicable to all levels of service, such as constant or variable bitrate real-time applications having tightly constrained packet delay,delay variation and cell loss requirements, as well as non-real-timeservice levels with more relaxed delay and cell loss requirements. Sincethe guaranteed admission and incremental bandwidth feature allocatesbandwidth to a call up to a maximum value, an explicit or implicitmaximum bandwidth is required for the call.

[0044] Although not required for the present invention, the network maysend control messages to the end user indicating the bandwidth initiallyand subsequently allocated to a guaranteed admission and incrementalbandwidth feature call. Most protocols send such control messages duringcall setup and in response to bandwidth change requests. The presentinvention may adapt existing practices in a protocol. ATM networks offerAvailable Bit Rate (ABR) service that provides calls access to unusedbandwidth. This service is implemented with call associated end-to-endcontrol loops that act as network feedback control mechanisms in whichnetwork nodes generate and update a continuous control message streamwith bandwidth information that the user terminals use to control theirtransmit rates. This mechanism could be adapted to provide informationto end terminals in an ATM network for guaranteed admission andincremental bandwidth feature calls.

[0045] The FIGURE shows a block diagram of a simplified generalembodiment of the present invention. User stations US1 and US2 areconnected to edge nodes NN1 and NN3, respectively. Network nodes NN1 andNN3 are further connected to network node NN2. Each network node NN1-NN3maintains a means LS1-LS3, respectively, to track guaranteed admissionand incremental bandwidth feature calls that have not been allocatedbandwidth up to their requested maximum. The means to track can include,but is not limited to, such mechanisms as tables, queues, lists, etc.

[0046] While the implementation details are protocol and vendorspecific, some exemplary embodiments for the H.323, SIP and ATMprotocols follow.

[0047] In an H.323 network, generally a call is started with anAdmission Request (ARQ) message from the user terminal followed by aSETUP message. The ARQ message would therefore be a logical place toinclude an indicator that the call is requesting guaranteed admissionand incremental bandwidth service. This indicator could be included, forexample, in the nonStandardData field of the ARQ message.

[0048] In certain situations, an H.323 call may be pre-granted admissionto the network, and an ARQ message may not be required. For these calls,the guaranteed admission and incremental bandwidth feature indicatorcould, for example, be included in the User-User information element ofthe SETUP message.

[0049] H.323 nodes would need to maintain a mechanism for trackingguaranteed admission and incremental bandwidth feature calls that havenot been allocated bandwidth up to the requested maximum. Each nodecould maintain a table of such calls, with an entry added at the time ofcall setup, for each guaranteed admission and incremental bandwidthfeature call passing through the node that has not been allocatedbandwidth up to the requested maximum. When the call has been allocatedthe requested maximum bandwidth, the associated entry in the table couldbe deleted.

[0050] As additional bandwidth is allocated to a call, notification tothe end user terminals could take place through transmission of BRQ orBCF messages from the gatekeeper to the user terminal referencing thecall with an updated bandwidth parameter.

[0051] In a SIP network, a session is initiated by the caller sending anINVITE message typically containing a session description written in SDPformat. The INVITE message would therefore be a logical place to includean indicator that the call is requesting guaranteed admission andincremental bandwidth service. This information could be included as asession attribute (“a=”) in the session description portion of theINVITE message. For example, a new session attribute of a=GABS ora=X−GABS could be defined.

[0052] SIP nodes would need to maintain a mechanism for trackingguaranteed admission and incremental bandwidth feature calls that havenot been allocated bandwidth up to the requested maximum. Each nodecould maintain a table of such calls, with an entry added at the time ofcall setup, for each guaranteed admission and incremental bandwidthfeature call passing through the node that has not been allocatedbandwidth up to the requested maximum. When the call has been allocatedthe requested maximum bandwidth, the associated entry in the table couldbe deleted.

[0053] As additional bandwidth is allocated to a call, notification ofthe end user terminals could take place through transmission ofadditional INVITE messages referencing the call with an updatedbandwidth parameter.

[0054] In an ATM network, each ATM cell packet contains a 5 byte headerand 48 bytes of payload. In the fourth byte of the header is the 3-bitPayload Type Identifier (PTI) field which is used to indicate the typeof information residing in the payload, and also for congestionnotification and OAM operations. Currently, code points 6 and 7 of thePTI (‘110’ b and ‘111’ b) are reserved for future functions. Forpurposes of the invention, one of these reserved values, for example‘111’ b, could be used to indicate that an ATM session is requestingguaranteed admission and incremental bandwidth service. Each ATM cellassociated with the session, from session setup through teardown, wouldhave a value of ‘111’ b in the PTI field indicating that the sessionwill use the guaranteed admission and incremental bandwidth servicefeature.

[0055] ATM nodes would need to maintain a mechanism for trackingguaranteed admission and incremental bandwidth feature sessions thathave not been allocated bandwidth up to the requested maximum. Each nodecould maintain a table of such sessions, with an entry added at the timeof session setup, for each guaranteed admission and incrementalbandwidth feature session passing through the node that has not beenallocated bandwidth up to the requested maximum. When the session hasbeen allocated the requested maximum bandwidth, the associated entry inthe table could be deleted.

[0056] As additional bandwidth is allocated to a call, notification ofthe end user terminals could take place through transmission of ResourceManagement (RM) messages referencing the call with an updated bandwidthparameter. RM messages are normally used with the Available Bit Rate(ABR) Service Category in end-to-end control loops that provide networkresource information to the user terminals. RM messages are allowed onall types of connections (although their use with non-ABR connections isnot defined), and their use can easily be adapted to the presentinvention as a means to provide network feedback to end-user terminalsusing the guaranteed admission and incremental bandwidth feature.

[0057] While the present invention has been shown and described withrespect to exemplary embodiments, it will be understood by those skilledin the art that modifications may be made thereto without departing fromthe scope and spirit of the invention. For example, while the guaranteedadmission and incremental bandwidth feature of the present invention ispresented in the context of the H.323, SIP and ATM protocols, theinvention is not limited to these protocols. The invention may beimplemented in any packet based protocol that allows for an admissioncontrol function partly or wholly based on requested and availablebandwidth. Also, while the preferred embodiments show the use ofspecific parameters, fields and messages for indicating that the call isa guaranteed admission and incremental bandwidth feature call, and forconveying bandwidth change information to the user stations, anysuitable parameter, field or message may be used. It is intended thatthe scope of the invention be defined by the claims appended hereto andtheir equivalents.

What is claimed is:
 1. A packet based network providing a guaranteedadmission and incremental bandwidth feature, a source user terminal anda destination user terminal connected to said network, the source userterminal transmitting a call setup message to said network requesting aconnection to the destination user terminal, the call setup messagecontaining an indicator that the call is a guaranteed admission andincremental bandwidth feature call, the call setup message containing anexplicit or implicit maximum bandwidth request, said network comprising:one or more network nodes; said network operated to establish a callpath between the source user terminal and the destination user terminalover said one or more network nodes; each of said one or more networknodes operated to recognize the guaranteed admission and incrementalbandwidth feature indicator in calls requesting the feature; each ofsaid one or more network nodes operated to preserve and convey theguaranteed admission and incremental bandwidth feature indicator in thecall setup message to the next network node in the call path; each ofsaid one or more network nodes operated to admit the guaranteedadmission and incremental bandwidth feature call to the network with aninitial bandwidth allocation that may be less than the maximum bandwidthrequested in the session setup message; each of said one or more networknodes operated to automatically incrementally allocate to the guaranteedadmission and incremental bandwidth feature call available userbandwidth up to the requested maximum bandwidth as bandwidth becomesavailable if the call was initially allocated less than the maximumbandwidth requested.
 2. A network according to claim 1, wherein one ofsaid one or more network nodes is further operated to perform asubscriber verification function.
 3. A network according to claim 1,wherein each of said one or more network nodes is further operated toallocate newly available user bandwidth to guaranteed admission andincremental bandwidth feature calls and to other calls based onequitable bandwidth allocation schemes.
 4. A network according to claim1, wherein each of said one or more network nodes is further operated totransmit control messages to the source and destination end userterminals indicating the bandwidth initially and subsequently allocatedto a guaranteed admission and incremental bandwidth feature call.
 5. Anetwork according to claim 1, wherein each of said one or more networknodes is further operated in accordance with the H.323 protocol.
 6. Anetwork according to claim 5, wherein the indicator that the call is aguaranteed admission and incremental bandwidth feature call is includedin the nonStandardData field of the Admission Request (ARQ) message. 7.A network according to claim 5, wherein the indicator that the call is aguaranteed admission and incremental bandwidth feature call is includedin the User-User information element of the SETUP message.
 8. A networkaccording to claim 5, wherein notification to the source and destinationend user terminals of additional bandwidth allocated to the call takesplace through transmission of Bandwidth Request (BRQ) messages to thesource and destination end user terminals referencing the call with anupdated bandwidth parameter.
 9. A network according to claim 5, whereinnotification to the source and destination end user terminals ofadditional bandwidth allocated to the call takes place throughtransmission of Bandwidth Confirm (BCF) messages to the source anddestination end user terminals referencing the call with an updatedbandwidth parameter.
 10. A network according to claim 1, wherein each ofsaid one or more network nodes is further operated in accordance withthe Session Initiation Protocol (SIP) and the Session DescriptorProtocol (SDP).
 11. A network according to claim 10, wherein theindicator that the call is a guaranteed admission and incrementalbandwidth feature call is included in the attribute (“a=”) field of theINVITE message.
 12. A network according to claim 10, whereinnotification to the source and destination end user terminals ofadditional bandwidth allocated to the call takes place throughtransmission of additional INVITE messages referencing the call with anupdated bandwidth (“b=”) parameter.
 13. A network according to claim 1,wherein each of said one or more network nodes is further operated inaccordance with Asynchronous Transfer Mode (ATM) protocol.
 14. A networkaccording to claim 13, wherein the indicator that the call is aguaranteed admission and incremental bandwidth feature call is includedPayload Type Identifier (PTI) field of the cell packet header.
 15. Anetwork according to claim 13, wherein notification to the source anddestination end user terminals of additional bandwidth allocated to thecall takes place through transmission of Resource Management (RM)messages referencing the call with an updated bandwidth parameter.
 16. Anetwork node providing a guaranteed admission and incremental bandwidthfeature in a packet based network, the network establishing a call paththat includes said network node between a source user terminal and adestination user terminal connected to the network and in response tothe source user terminal transmitting a call setup message to thenetwork requesting a connection to the destination user terminal, thecall setup message containing an indicator that the call is a guaranteedadmission and incremental bandwidth feature call, the call setup messagecontaining an explicit or implicit maximum bandwidth request, saidnetwork node comprising: functionality operated to recognize theguaranteed admission and incremental bandwidth feature indicator incalls requesting the feature; functionality operated to preserve andconvey the guaranteed admission and incremental bandwidth featureindicator in the call setup message to the next network node in the callpath; functionality operated to admit the guaranteed admission andincremental bandwidth feature call to the network with an initialbandwidth allocation that may be less than the maximum bandwidthrequested in the session setup message; functionality operated toautomatically incrementally allocate to the guaranteed admission andincremental bandwidth feature call available user bandwidth up to therequested maximum bandwidth as bandwidth becomes available if the callwas initially allocated less than the maximum bandwidth requested.
 17. Anetwork node according to claim 16, wherein said network node is furtheroperated to perform a subscriber verification function.
 18. A networknode according to claim 16, wherein said network node is furtheroperated to allocate newly available user bandwidth to guaranteedadmission and incremental bandwidth feature calls and to other callsbased on an equitable bandwidth allocation scheme.
 19. A network nodeaccording to claim 16, wherein said network node is further operated totransmit control messages to the source and destination end userterminals indicating the bandwidth initially and subsequently allocatedto the guaranteed admission and incremental bandwidth feature call. 20.A network node according to claim 16, wherein said network node isfurther operated in accordance with the H.323 protocol.
 21. A networknode according to claim 20, wherein the indicator that the call is aguaranteed admission and incremental bandwidth feature call is includedin the nonStandardData field of the Admission Request (ARQ) message. 22.A network node according to claim 20, wherein the indicator that thecall is a guaranteed admission and incremental bandwidth feature call isincluded in the User-User information element of the SETUP message. 23.A network node according to claim 20, wherein notification to the sourceand destination end user terminals of additional bandwidth allocated tothe call takes place through transmission of Bandwidth Request (BRQ)messages to the source and destination end user terminals referencingthe call with an updated bandwidth parameter.
 24. A network nodeaccording to claim 20, wherein notification to the source anddestination end user terminals of additional bandwidth allocated to thecall takes place through transmission of Bandwidth Confirm (BCF)messages to the source and destination end user terminals referencingthe call with an updated bandwidth parameter.
 25. A network nodeaccording to claim 16, wherein said network node is further operated inaccordance with the Session Initiation Protocol (SIP) and the SessionDescriptor Protocol (SDP).
 26. A network node according to claim 25,wherein the indicator that the call is a guaranteed admission andincremental bandwidth feature call is included in the attribute (“a=”)field of the INVITE message.
 27. A network node according to claim 25,wherein notification to the source and destination end user terminals ofadditional bandwidth allocated to the call takes place throughtransmission of additional INVITE messages referencing the call with anupdated bandwidth (“b=”) parameter.
 28. A network node according toclaim 16, wherein said network node is further operated in accordancewith Asynchronous Transfer Mode (ATM) protocol.
 29. A network nodeaccording to claim 28, wherein the indicator that the call is aguaranteed admission and incremental bandwidth feature call is includedPayload Type Identifier (PTI) field of the ATM cell packet header.
 30. Anetwork node according to claim 28, wherein notification to the sourceand destination end user terminals of additional bandwidth allocated tothe call takes place through transmission of Resource Management (RM)messages referencing the call with an updated bandwidth parameter.
 31. Amethod in a network node for providing a guaranteed admission andincremental bandwidth feature in a packet based network, the networkestablishing a call path that includes said network node between asource user terminal and a destination user terminal connected to thenetwork and in response to the source user terminal transmitting a callsetup message to the network requesting a connection to the destinationuser terminal, the call setup message containing an indicator that thecall is a guaranteed admission and incremental bandwidth feature call,the call setup message containing an explicit or implicit maximumbandwidth request, said method comprising: recognizing the guaranteedadmission and incremental bandwidth feature indicator in callsrequesting the feature; preserving and conveying the guaranteedadmission and incremental bandwidth feature indicator in the call setupmessage to the next network node in the call path; admitting theguaranteed admission and incremental bandwidth feature call to thenetwork with an initial bandwidth allocation that may be less than themaximum bandwidth requested in the session setup message; allocatingautomatically and incrementally to the guaranteed admission andincremental bandwidth feature call newly available user bandwidth up tothe requested maximum bandwidth as bandwidth becomes available if thecall was initially allocated less than the maximum bandwidth requested.32. A method according to claim 31, further comprising performing asubscriber verification function.
 33. A method according to claim 31,further comprising allocating newly available user bandwidth toguaranteed admission and incremental bandwidth feature calls and toother calls based on an equitable bandwidth allocation scheme.
 34. Amethod according to claim 31, further comprising transmitting controlmessages to the source and destination end user terminals indicating thebandwidth initially and subsequently allocated to the guaranteedadmission and incremental bandwidth feature call.
 35. A method accordingto claim 31, wherein the network node is operated in accordance with theH.323 protocol.
 36. A method according to claim 35, wherein theindicator that the call is a guaranteed admission and incrementalbandwidth feature call is included in the nonStandardData field of theAdmission Request (ARQ) message.
 37. A method according to claim 35,wherein the indicator that the call is a guaranteed admission andincremental bandwidth feature call is included in the User-Userinformation element of the SETUP message.
 38. A method according toclaim 35, wherein notification to the source and destination end userterminals of additional bandwidth allocated to the call takes placethrough transmission of Bandwidth Request (BRQ) messages to the sourceand destination user terminals referencing the call with an updatedbandwidth parameter.
 39. A method according to claim 35, whereinnotification to the source and destination end user terminals ofadditional bandwidth allocated to the call takes place throughtransmission of Bandwidth Confirm (BCF) messages to the source anddestination user terminals referencing the call with an updatedbandwidth parameter.
 40. A method according to claim 31, wherein saidnetwork node is further operated in accordance with the SessionInitiation Protocol (SIP) and the Session Descriptor Protocol (SDP). 41.A method according to claim 40, wherein the indicator that the call is aguaranteed admission and incremental bandwidth feature call is includedin the attribute (“a=”) field of the INVITE message.
 42. A methodaccording to claim 40, wherein notification to the source anddestination end user terminals of additional bandwidth allocated to thecall takes place through transmission of additional INVITE messagesreferencing the call with an updated bandwidth (“b=”) parameter.
 43. Amethod according to claim 31, wherein said network node is furtheroperated in accordance with Asynchronous Transfer Mode (ATM) protocol.44. A method according to claim 43, wherein the indicator that the callis a guaranteed admission and incremental bandwidth feature call isincluded Payload Type Identifier (PTI) field of the ATM cell packetheader.
 45. A method according to claim 43, wherein notification to thesource and destination end user terminals of additional bandwidthallocated to the call takes place through transmission of ResourceManagement (RM) messages referencing the call with an updated bandwidthparameter.